1. Field of the Invention
The present invention relates to an image forming apparatus which has an energy-saving mode, a normal mode, and a control method thereof.
2. Description of the Related Art
In the conventional image forming apparatus, an authentication is performed by an identification (ID) card which stores a user's identification information, and the user who is correctly authenticated is allowed to use the image forming apparatus. Accordingly, the apparatus can be managed and security is enhanced.
For purposes of saving energy, the image forming apparatus includes an energy-saving mode (also referred to as power-saving mode or sleep mode) for shutting down electric power supply to some parts of the image forming apparatus. When user authentication is performed under the energy-saving mode, the image forming apparatus recovers from the energy-saving mode to the normal mode. (For instance, see Japanese Patent Application Laid-Open No. 2006-47765)
In a technique discussed in Japanese Patent Application Laid-Open No. 2006-47765, since a controller of an image forming apparatus main body performs the user authentication after detecting an ID card, a power supply to the controller needs to be maintained even during the energy-saving mode. As a result, further power saving cannot be achieved.
Another power savings issue can arise if user authentication fails. For example, if the image forming apparatus only performs detection of the ID card under the energy-saving mode, the image forming apparatus recovers from the energy-saving mode to the normal mode in response to detection of the ID card and then performs the user authentication using an external authentication apparatus after recovering to the normal mode. In this example, there is no power use issue if the authentication succeeds since the user will be allowed to operate the image forming apparatus. In the event the user authentication fails, since the image forming apparatus still needed to recover from the energy-saving mode, unnecessary power is consumed until the image forming apparatus shifts back to the energy-saving mode.
In addition, components of the image forming apparatus which have an upper limit for a number of activations will uselessly consume their lifetime because the image forming apparatus unnecessarily recovers from the energy-saving mode. Such components include, but are not limited to, a hard disk (HDD), a relay which turns electric power supply on/off in a power supply unit, and a fuse used in the power supply unit.